Labyrinth seals are often used as air-oil seals to provide sealing of rotating shafts of bearing compartments and gear cases, etc. Labyrinth seals typically comprise knife edges or teeth or fins which rotate relative to a surrounding seal land or runner, the knife edges having tight tip clearances with a surface of the land or runner. The relative rotation between the knife edges and the runner of labyrinth seals, however, can tend to cause rubbing wear on the runner surface, which can eventually lead to particles of the runner being shaved off and ingested into an adjacent bearing supporting the shaft. Knife edge wear also results. These rubs can significantly reduce the sealing capability and ingested particles can also damage bearings, gears and/or other components adjacent to such seal if these components ingest the particles. Polymers, for example, are avoided as runners because they rub easily and the polymeric particles could adversely effect bearings, gear surfaces, etc.
An improved seal runner surface for a labyrinth seal is therefore desired, particularly for use as a shaft seal.